Articular cartilage is a highly organized avascular tissue composed of chondrocytes formed in an extracellular matrix. This tissue is extremely important to the normal, healthy function and articulation of joints. Articular cartilage enables joint motion surfaces to articulate smoothly with a very low coefficient of friction. It also acts as a cushion to absorb compressive, tensile, and shearing forces and, thus, helps protect the ends of bone and surrounding tissue.
Injuries and defects to articular cartilage are frequent. Traumatic chondral injuries, for example, are common in sports and other activities that cause severe stress and strain to joints. Osteoarthritis is also a common condition that develops as cartilage wears, weakens, and deteriorates at the joint motion surfaces of bones.
Unfortunately, articular cartilage is generally thin with an extremely low or insignificant blood flow and, as such, has a very limited ability to repair or heal itself. Partial-thickness chondral defects, for example, cannot spontaneously heal. If these defects are left untreated, they often degenerate at the articular surface and progress to osteoarthritis. Full-thickness defects that penetrate subchondral bone can undergo some spontaneous repair if fibrocartilage forms at defect. Even in spite of the formation of fibrocartilage, clinical evidence shows that full-thickness defects continue to degenerate and progress to osteoarthritis if these defects are left untreated.
Early diagnosis and treatment are crucial to hindering or stopping the progression of arthritis and degeneration of articular cartilage at joint motion surfaces. Today, depending on the grade of chondral damage, patients usually have several surgical options to repair or regenerate articular cartilage.
For small injuries, such as partial-thickness defects, a patient can be treated with a palliative procedure using known lavage and debridement techniques. These techniques remove loose debris and smooth shredded or frayed articular cartilage. Although this arthroscopic technique is common, relief for the patient can be incomplete and temporary.
Osteochondral autologous transplantation (OATS) and autologous chondrocyte implantation (ACI) are two other treatment modalities used to treat larger or more severe articular defects.
In OATS, cartilage is removed from a normal, healthy location and transferred or planted to the defective area. This procedure is inherently limited to the amount or availability of healthy autologous osteochondral grafts in the patient. Spaces between graft plugs and lack of integration with donor and recipient hyaline cartilage are other clinical concerns with OATS.
In ACI, articular cartilage cells are arthroscopically removed or harvested from the patient and sent to a laboratory. Here, the cells are cultured and multiplied. The newly grown chondrocytes are then re-implanted back into the patient at the defected area. The process of growing cells outside the patient can be expensive. Further, this procedure can require a relatively larger incision to place the cartilage cells. What's more, several years may be required for the implanted cells to mature fully.
Microfracture is another treatment modality used to treat articular defects. This technique is a marrow stimulating arthroscopic procedure to penetrate the subchondral bone to induce fibrin clot formation and the migration of primitive stem cells from the bone marrow into the defective cartilage location. More particularly, the base of the defective area is shaved or scraped to induce bleeding. An arthroscopic awl or pick is then used to make small holes or microfractures in the subchondral bone plate. The end of the awl is manually struck with a mallet to form the holes while care is made not to penetrate too deeply and damage the subchondral plate. The holes penetrate a vascularisation zone and stimulate the formation of a fibrin clot containing pluripotential stem cells. The clot fills the defect and matures into fibrocartilage.
Microfracturing the subchondral bone plate can be a successful procedure for producing fibrocartilaginous tissue and repairing defective articular cartilage. The current procedure or method for performing the surgical technique, though, has some disadvantages.
As one disadvantage, the microfractures or holes are made when the surgeon manually strikes or otherwise forces the awl into the subchondral bone plate. Specifically, the holes are manually created. Manually created holes in the bone plate can have inconsistent depths depending on the force applied to the awl. If the holes are not deep enough, then the formation of the fibrin clot may not occur. On the other hand, if the holes are too deep, then the subchondral bone plate can be damaged and lead to unwanted consequences and complications. The depth of the holes, thus, depends on the skill of the surgeon to accurately and consistently hit the end of the awl and force it to the correct depth in the bone plate.
As another disadvantage, many microfractures may be placed in a single surgery. Each hole must be manually placed, and the creation of the many holes can take a lot of time during the surgery. Depending on the size of the defect being treated, 25–100 or more holes could be required. Several hours may be required to place manually each of these holes.
As yet another disadvantage, the microfractures should be placed 3 to 4 millimeters apart from each other on the bone plate. The placement of these holes and distance between adjacent holes, then, depends on the visual judgment and skill of the surgeon.
It therefore would be advantageous to provide a new method for performing the microfracture surgical technique. Such method would eliminate the disadvantages associated with conventional microfracture surgery.